Dimensional crossover transition in a system of weakly coupled superconducting nanowires

Abstract

Owing to recent observations of superconductivity in quasi-onedimensional (1D) systems, Josephson arrays composed of aligned and weakly coupled 1D superconducting nanowires have attracted renewed interest for modeling the experimental data. Carrying out Monte Carlo simulations, we go beyond the traditional mean field results to show that the competition between 1D fluctuations and the transverse Josephson coupling between the nanowires can lead to a 1D-3D crossover transition at a temperature T c below the mean field T O C of the wires, with interesting and surprising pre-transitional characteristics. In particular, the specific heat exhibits a rounded peak between T c and T O C , and the phase correlation length within the transverse ab plane diverges at T c from above, in a manner consistent with that of a 2D Berezinskii-Kosterlitz-Thouless 4 These authors contributed equally to this work.

Reentrant Phase Coherence in Superconducting Nanowire Composites

“…24,26,29,[34][35][36][37][38][39][40] Na 2−δ Mo 6 Se 6 is not an inhomogeneous or granular superconductor in the traditional sense, where phase coherence is determined by the ratio of E J to E C for individual grains. 31,32 Instead, it is a crystalline superconductor whose normal state is a localized metal, due to the combination of Na vacancy disorder and intense 1D anisotropy. Signatures of localization are clearly visible in the normal-state resistance R NS , which diverges as T → 0 and displays a large negative magnetoresistance ( Fig.…”

“…Although Berezinskii-Kosterlitz-Thouless (BKT) transitions are generally considered to be a property of 2D materials, evidence for BKT-type behavior has been reported in experimental and numerical studies of q1D superconductors. 11,12,30,31 In Fig. S4(a), we sketch the spatial variation of the phase of the superconducting order parameter on each (Mo 6 Se 6 ) ∞ filament in a crosssectional "slice" perpendicular to the c (high-symmetry) axis.…”

Electron–electron interactions of the multi-Cooper-pairs in the 1D limit and their role in the formation of global phase coherence in quasi-one-dimensional superconducting nanowire arrays

“…This phase ordering transition triggers a dimensional crossover in the array from a 1D fluctuating superconducting state with finite resistance at high temperatures to a zero-resistance 3D bulk phase-coherent superconducting state in the low temperature regime. It has been shown that this transition falls into the same universality class as the famous Berezinski-Kosterlitz-Thouless (BKT) transition [22,23,24] in 2D superconducting systems [6], where a vortex-unbinding transition occurs through vortex excitations in the phases of the order parameters in groups of adjacent nanowires [3,4]. The Josephson phase current, which establishes the BKT-type transverse coupling, is very weak when the tunneling barrier is thick or the coherence length is short.…”

“…Quasi-1D superconductors represent intriguing materials that allow investigating quantum confinement effects, strong phase fluctuations, and critical phenomena, based on the fact that arrays of dense superconducting atomic chains or nanowires represent intrinsic Josephson junction arrays with unique critical phase transition behavior [1,2,3,4,5,6,7]. Of particular interest is the observation that under certain conditions the upper critical fields (Hc2) can be strongly enhanced with Hc2 values reaching up to a factor 200 of the value of the corresponding materials in their bulk form, and significant critical temperature (Tc) enhancements compared to the bulk state [1,2].…”

Superconducting versus semiconducting electronic ground state in chirality-specific double-wall carbon nanotubes

“…More recently, it has been shown that if one takes into account the dielectric screening effect of the nanotube array (on the electron-electron interaction), a superconducting ground state can indeed be realized in (5,0) carbon nanotubes [23][24][25]. Furthermore, theoretical Monte Carlo simulations on the Ginzburg-Landau model have shown that with the appearance of the superconducting condensate, even a very weak Josephson coupling between the aligned nanotubes can lead to a 1D to 3D (three-dimensional) crossover transition at a temperature below that where the superconducting condensate first appears [8,26].…”